Process for manufacturing acrylic synthetic fiber containing foams therein



1963 HIROSHI UCHIYAMA ETAL 3,112,162

PROCESS F OR MANUFACTURING ACRYLIC SYNTHETIC FIBER CONTAINING FOAMS THEREIN Filed Nov. 5, 1962 I 5 Sheets-Sheet 1 N v E N TO R s H/ROSH/ UCH/ VA MA YA Sl/Hl/PO Mz/RA KAN! 14/050 6A KA ATTORNEY 1963 HIROS UCHIYAMA ETAL 3,112,162

PROCESS FOR MA ACTUR G ACR L C SYNTHETIC FIBER CONTAININ OAMS EREIN Filed Nov. 5, 1962 3 Sheets-Sheet 2 v qvv My I 0 up;

to be continued myENTo f C EOSH/ 001/ YA yAsz/f 0 NORA/04A H1 0 .FAKA/ 1 BY A'ITORNEY Nov. 26, 1963 Filed NOV. 5, 1962 HIROSHI UCHIYAMA ETAL PROCESS FOR MANUFACTURING ACRYLIC SYNTHETIC FIBER CONTAINING FOAMS THEREIN 5 Sheets-Sheet 5 Fig. 3 (continued) U D F D F Exs L. C. TC. L. C. 'l'. C.

M 4:; 1 0; 9 Q'OCQQOO ."hv'f' Q) I8 6 ."y'w' Q? @3 2o '33:" @E4 6? .J. @523 BY Y ATTORNEY United States Patent PROCESS FOR MANUFACTURING ACRYLIC SYN- THETIC FIBER CQNTAINENG FGAMS 'IHEREKN I-liroshi Uchiyama, Yasuhiro Murakami, and Hideo Sakai,

Ohtsu-shi, Shiga-ken, Japan, assignors to Toyo Rayon Kabushiki Kaisha, Tokyo, Japan, a corporation of .iapan Filed Nov. 5, 1962, Ser. No. 235,215 Claims priority, application Japan Nov. 8, 1961 6 Claims. (Cl. 1854-) This invention relates to a process for manufacturing acrylic synthetic fiber containing foams therein.

Because fibers containing foams therein have low apparent specific gravity, the use of such fibers as a sort of bulky yarn has been encouraged in order to make the products varied.

Generally, in order to obtain fibers containing foams therein by wet spinning, a method comprising a step of mixing a substance to produce gas by reacting with the component in a coagulating bath with a spinning solution is considered. Heretofore, with reference to rayons, the process for manufacturing fibers containing foams therein by a sodium carbonate-sulfuric acid system has been well known. However, with reference to synthetic fibers, because no commercially sutiicient production speed was obtained or the product obtained was apt to become translucent or opaque, any combination of a polymer spinning solution, a coagulating bath and a foaming agent which could successfully achieve the purpose has not been proposed.

According to this invention, acrylic synthetic fiber containing foams therein can be manufactured by mixing at least one kind of isocyanate with a spinning solution containing substantially no water for wet spinning acrylic synthetic fiber, spinning the mixture into a coagulating bath consisting of a water-solvent system to form filaments and thereafter drawing the filaments.

The term acrylic synthetic fiber used in the specification and claims of this application means the synthetic fiber manufactured from a polymer containing at least 85 mol percent of acrylonitrile unit. The spinning solution used in this invention may be an acrylic polymer dissolved in a solvent, and may also be the reaction mixture obtained 'by polymerizing a suitable acrylic-containing monomer in a solvent. The spinning solution used in this invention necessarily contains substantially no water. If there is some water in the spinning solution, upon mixing isocyanate therewith, not only the water would react therewith and isocyanate would be consumed, but also the spinning might become difficult because of foams formed in the spinning solution before spinning. The solvent suitable for the preparation of the spinning solution may be any solvent ordinarily used in spinning solutions for Wet spinning acrylic synthetic fiber. The solvent must not have any radical which would react with isocyanate under operating conditions. As examples of the solvent suitable for the preparation of the spinning solution of this invention, there are dimethylformamide, diethylformamide, dimethylacetamide, diethylacetamide, ethylene carbonate, dimethylsulfoxide, y-butyrolactone and acetone. The concentration of polymer in the spinning solution is -27% by weight, preferably 19-20% by weight.

Examples of isocyanates used as the foaming agent in the process of this invention are tolylene diisocyan ate, phenylisocyanate, ethylisocyanate, hexamethylene diisocyanate, diphenylmethanediisocyanate, naphthylene diisocyanate, nitrodiphenyl diisocyanate and diphenylsulfondiisocyanate, etc. The amount of isocyanate used is within the range of 0.5100% by weight, preferably 10-50% by weight, *based on the amount of polymer in the spinning solution. When an amount less than 0.5% is used,

3 ,il2,lfi2 Patented Nov. 2d, 1963 ice the desired result cannot be achieved. When isocyanate in the amount of more than 100% based on that of the polymer is used, generally the spinning solution undergoes gelation. The isocyanate may be mixed with the spinning solution under normal atmosphere, but preferably the mixing is conducted under pressure. When a slight amount of water and a substance such as an acid, used as the color prevention agent of the spinning solution, exist in the spinning solution, upon the mixing of the isocyanate with the spinning solution, the isocyanate reacts with said substance in the spinning solution, forming a great amount of foams which makes the spinning extremely difiicult. Accordingly, said mixing is preferably carried out under such pressure as would inhibit the formation of foam.

In the process of this invention, as the coagulating bath a water-solvent system is used. As the solvent in such systems, dimethylformamide, diethylformamide, dimethylace-tarnide, diethylacetamide, e t h y 1 e n e carbonate, -butyrolactone, tetnahydrofuran, acetone, dioxane, methanol, ethanol, butanol, propanol and thioglycolic acid may be utilized. It is advantageous to make the solvent of the coagulating bath the same as the solvent used for preparing the spinning solution.

When isocyanate reacts with the water-solvent system, foam (carbon dioxide) is not necessarily always formed immediately. Referring to the attached drawings, FIGS. 1 and 2 illustrate the immediately foaming zone of the isocyanate-solvent-water system. In the drawings, TDI stands for tolylene diisocy anate, PI stands for phenylisocyanate, DMSO stands for :dimethylsulfoxide and W stands for water. The point P in FIG. 1 stands for a system comprising a percent of tolylene diisocyanate, b percent of dimethylsulfoxide and 0 percent of water. The composition of a system capable of immediately foaming at 30 C. is expressed by points inside the hatched zones in FIG. 1 and FIG. 2. As will be apparent from these drawings, dimethylsulfoxide has a capacity to promote the reaction between water and isocyanate. Such a phenomenon is observed with reference to other solvents, such as cited above, and isocyanate. In a coagulating bath containing less than 30% by weight of a solvent, the speed of reaction between isocyanate in the spinning solution and water in the coagulating bath is not sufficiently fast. Because of this the production speed is low and the use of such coagulating bath is unsuitable for mass production. Furthermore, the inclination of the product to become translucent or opaque is observed.

On the other hand, in a coagulating bath containing more than 70% by weight of a solvent, isocyanate and water immediately react with each other, emitting carbon dioxide. However, because the 'cogulating force of molecules in the filament is very weak, the foam remains in the filament, and it is impossible to obtain the desired product. Accordingly, the amount of the solvent contained in the coagulating bath used in this invention is preferably 30 70% by weight. The temperature of the coagulating bath may vary from 5 to C.

The spun filament with foams being formed inside is drawn to 27 times the original length by a conventional filament drawing process. When the drawing ratio is smaller than 2, the physical property of the product is unsatisfactory, while on the other hand, when it is larger than 7, the foams inside the filament are apt to disappear. For the purpose of preventing the foams from disappearing, it is preferable to draw the filament after the microstructure of the filament is nearly established.

In a preferred mode of this invention, it is possible to treat the filament in a relaxed state by steam before carrying out the finishing treatment such as drying the filament after it is drawn. Ordinarily, the relaxation ratio (ratio of the difference between the feeding speed and the rolling speed of the filament to the rolling speed) varies -30%. By carrying out the steam treatment, it is possible to decrease the inclination for the foam to disappear at the time of drying.

According to the process of this invention, it is possible to obtain the desired fibers containing foams therein having low apparent density and sufiiciently high tensile strength at the desired production speed and to make varied products of acrylic synthetic fiber by only slightly changing the existing procedures and conditions for manufacturing acrylic synthetic fiber by wet spinning.

The following examples are described for the purpose of exemplifying this invention.

EXAMPLE 1 As the spinning solution a dimethylsulfoxide solution containing 19 percent by Weight of a copolymer consisting of 95.7 mol percent of acrylonitrile and 4.3 mol percent of methyl acrylate and 1 percent by weight of oxalic acid, but containing substantially no water (having a viscosity of 207 poises at C.) was used. To said spinning solution, tolylene diisocyanate was added and mixed as a foaming agent under the gauge pressure of 2-3 kg/ cm. until the amount thereof became 5% by weight of the spinning solution (26% by weight of the copolymer).

The spinning solution was spun through a spinneret having orifices of a diameter of 0.08 mm. into a coagulating bath consisting of 55% by Weight water and by weight dimethylsulfoxide at a temperature 25 C. The immersion length of the spun filaments was 120 cm., and the spun filaments were taken out of the coagulating bath at a rolling speed of 3 m./min. The immersion length of the resulting filaments was made cm. in water at a temperature of 95-100 C., and the resulting filaments were then drawn to about 5 times the original length. The resulting drawn filaments at an immersion length of 200 cm. were passed through water of 25 C. and washed. The washed filaments were treated with saturated steam at 100 C. under a relaxation ratio of 25%. The steam treated filaments were heat treated at 120 C. for 6 minutes.

The longitudinal and the transverse cross sections of the undrawn filament and the drawn filament obtained by the process of this example are shown in FIG. 3, wherein Exs. stands for example, UDF stands for undrawn filament, DP stands for drawn filament and TC stands for transverse cross section. (Same can be said of the following other examples.)

The dry tensile strength, dry elongation, knot strength and knot strength ratio of the final product were 1.92 g./d., 34.5%, 1.17 g./d. and 96%, respectively.

EXAMPLES 2-5 With the exception of using the following isocyanates described in Table 1 instead of tolylene diisocyanate the procedure of Example 1 was repeated and similar products, nearly same products as in Example 1 were obtained. The dry tensile strength and dry elongation of the products obtained are shown in Table 1.

Table 1 The longitudinal and the transverse cross sections of the undrawn filament and the drawn filament are shown in FIG. 3.

EXAMPLES 6-11 Except making the amounts of tolylene diisocyanate used as the foaming agent those described in the follow- Table 2 Example Adding amount Dry tensile Dry elongation of TDI strength (g./d.) (percent) 1 Weight percent of tolylene diisocyanate based on the polymer The longitudinal and the transverse cross sections of the undrawn filaments and the drawn filaments obtained in Examples 6-11 are shown in FIG. 3. As will be seen in FIG. 3, when the amount of isocyanate used is small as in Examples 6 and 7, the forming of foams is apt to be insuflicient.

EXAMPLE 12 With the exceptions of making the contents of dimethylsulfoxide in the coagulating bath and the temperatures of the bath those mentioned in the following Table 3, the procedures and conditions described in Example 1 were repeated and the filaments containing foams shown in Exs. 13-21 of FIG. 3 were obtained.

Table 3 Example DMSO-contents Temperature (percent) 1 of the bath C.)

1 Weight percent of dirnethylsulfoxidc in the coagulating bath The apparent specific gravity of the products obtained by each of the aforementioned examples was within the range of about 0.8-1.0.

What is claimed is:

1. Process for manufacturing acrylic synthetic fiber containing foams therein which comprises mixing at least one kind of isocyanate with a spinning solution of an acrylic synthetic polymer containing substantially no water, spinning the mixture into an aqueous coagulating bath containing spinning solvent, and drawing the spun filaments.

2. Process described in claim 1, wherein at least one kind of isocyanate selected from the group consisting of tolylene diisocyanate, phenylisocyanate, ethylisocyanatc, hexamethylene diisocyanate, diphenylmethanediisocyanate, naphthylene diisocyanate, nitrodiphenyl diisocyanate and diphenylsulfondiisocyanate is mixed in the amount of 0.5- percent by Weight based on the polymer in the spinning solution.

3. Process described in claim 2, wherein a system consisting of 30-70 percent by weight of water and 70-30 percent by weight of a solvent is used as a coagulating bath.

4. Process described in claim 3, wherein at least one compound selected from the group consisting of dimethylformamide, diethylformamide, dimethylacetamide, diethylacetamide, ethylene carbonate, q butyrolactone, tetrahydrofuran, acetone, dioxane, methanol, ethanol, butanol, propanol and thioglycolic acid is used as a solvent of the coagulating bath.

5. Process for manufacturing acrylic synthetic fiber containing foams therein which comprises mixing at least one kind of isocyanate with a spinning solution of an acrylic synthetic polymer containing substantially no water, spinning the mixture into an aqueous coagulating bath containing spinning solvent, thereafter drawing the spun filaments and treating the drawn filaments by steam in a relaxed state.

6. Process for manufacturing acrylic synthetic fiber containing foams therein which comprises mixing at least one kind of isocyanate in a 10-27 weight percent spinning solution of an acrylic polymer, containing at least 85 mol percent of acrylonitrile unit, in dimethylsulfoxide, said isocyanate being mixed in an amount of 10-15 percent by weight based on the polymer in said solution, spinning said mixture into a coagulating bath consisting of 3 070 percent by weight of water and 70-30 percent by weight of dimethylsulfoxide, drawing the resulting filaments, and thereafter treating the drawn filament in a relaxed state with steam.

References Cited in the file of this patent UNITED, STATES PATENTS 3,015,873 Dietzach et a1. Jan. 9, 1962 

1. PROCESS FOR MANUFACTURING ACRYLIC SYNTHETIC FIBER CONTAINING FOAMS THEREIN WHICH COMPRISES MIXING AT LEAST ONE KIND OF ISOCYANATE WITH A SPINNING SOLUTIN OF AN ACRYLIC SYNTHETIC POLYMER CONTAINING SUBSTANTIALLY NO WATER, SPINNING THE MIXTURE INTO AN AQUEOUS COAGULATING BATH CONTAINING SPINNING SOLVENT, AND DRAWING THE SPUN FILAMENTS. 